No audio between extensions on internal network

[James Avey]

We have a hosted 3CX instance. We have provisioned some physical phones using direct STUN so the phones can be used remotely if required. Calls between extensions work fine when one phone is outside the office network and one phone inside. However, calls between extensions on the internal network connect but have no audio. The firewall provider says that no internal network traffic is blocked. Also, the firewall is not SIP ALG capable. In this scenario, does the audio stream travel up and down to the hosted 3CX instance, or as peer to peer traffic on the internal network? Does anyone have any ideas why this could happen? Many thanks.

 

[Charles_3CX]

Please note we do not support phones provisioned remotely via STUN. There are too many network variables to consider with this provisioning method. Therefore, we only support and advise when provisioning is via the 3CX SBC.

This is also mentioned in the guide under the Requirements / Limitations section: https://www.3cx.com/ordering/pricing/hosted-info/

 

[MCCDCHS]

We have a hosted 3CX instance. We have provisioned some physical phones using direct STUN so the phones can be used remotely if required. Calls between extensions work fine when one phone is outside the office network and one phone inside. However, calls between extensions on the internal network connect but have no audio. The firewall provider says that no internal network traffic is blocked. Also, the firewall is not SIP ALG capable. In this scenario, does the audio stream travel up and down to the hosted 3CX instance, or as peer to peer traffic on the internal network? Does anyone have any ideas why this could happen? Many thanks.

I've frequently run into this issue. Its been the switches / firewall every time.

Ubiquiti hardware is the main culprit in most of our cases. Even when the firewall had all the correct ports / SIP / ALG it sometimes would do this.

One way to Test was to turn off the firewall. THEN POWER CYCLE IT! We found - if using ubiquiti the gateways even when set to allow would still drop the traffic. Once we turned off the firewall sometimes they still would drop the traffic. Then we hard powered the unit and it would work fine. Turned on the firewall and issue started up again.

Not sure what hardware your using - would recommend providing more details.
If your hosted, yes your calls go out then back in.
If your internal the calls do go to the server and back. It's got to be a firewall issue with the switch most of the time. Aruba Network equipment has no issues with 3cx and routing. I didn't even have to configure a thing. Can't tell you how many weeks I beat my head against a wall using ubiquiti firewalls.

Easy Test - Take a backup of your firewall settings. Then turn it OFF> See if it works.
Also I assume you did all the standard is port X open ect. stuff as posted on the guides.